import turtle as t
t.setup(660,660)
t.bgpic("./夜空.gif")
t.penup()
t.goto(-300,300)
t.pendown()
t.pencolor("yellow")
size = 5 # 画笔的大小
while size < 50:
    t.pensize(size)
    t.forward(20)
    size = size+1
    t.right(1)
t.done()